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Toronto, September 19, 2016

By Geoff Koehler

Dr. Warren Lee looks at a collection of endothelial cells
Dr. Warren Lee looks at a collection of endothelial cells in his Keenan Research Centre for Biomedical Science lab. Dr. Lee has developed a microscope technique that allows scientists to see how molecules such as cholesterol and insulin escape the blood stream and get into other areas of the body. (Photo by Yuri Markarov)

In Dr. Warren Lee’s lab, cholesterol molecules pass through a blood vessel cell and twinkle like stars against the night sky. Some cholesterol flashes brilliantly — shooting stars burning bright and fading just as quickly — while others gradually dim or disappear altogether.

Dr. Lee’s is the first lab in the world to see this light show for the purpose of studying how cholesterol or other molecules find their way through the endothelium — the blood vessel wall’s innermost lining.

“Until now, it’s been hard for researchers to see how things move through endothelial cells,” said Dr. Lee, a researcher with St. Michael’s Hospital’s Keenan Research Centre for Biomedical Science and a physician in the Medical-Surgical Intensive Care Unit.

“Better understanding of how molecules get behind blood vessel cells could one day help researchers reduce cholesterol buildup that causes blocked arteries, improve insulin levels and blood sugar control for those with diabetes, or prevent tissue edema such as occurs during severe lung injury in critically ill patients.”

VIDEO: In Dr. Warren Lee’s lab, cholesterol molecules pass through a blood vessel cell and twinkle like stars against the night sky. Some cholesterol flashes brilliantly — shooting stars burning bright and fading just as quickly — while others gradually dim or disappear altogether.
Dr. Lee discovered a new use for a microscope that’s been around since the 1980s. With the microscope, which uses a technique called total internal reflection fluorescence, or TIRF, Dr. Lee can, for the first time, observe cholesterol or other molecules getting transported through endothelial cells in real time.

In his lab, Dr. Lee simulated the innermost layer of a blood vessel’s lining by filling a Petri dish with a single layer of endothelial cells. His lab team placed fluorescent-dyed molecules, such as cholesterol or insulin, on top of the layer of cells and then focused the TIRF microscope on the bottom of the dish. With the TIRF microscope, researchers could see the bright flourescent molecules exiting the bottom of the cell.

“We’ve used TIRF to study how large molecules, such as LDL (or bad) cholesterol, get out of the blood stream and into other parts of the body,” said Dr. Lee. “In a process called transcytosis, vesicles (a fluid- or air-filled sac) in the endothelial cell act like a taxi for molecules in the blood stream, picking them up and dropping the molecules off on the other side of the blood vessel wall.”

   
Dr. Lee was the lead on a successful $1-million CIHR grant that will bring a TIRF microscope to St. Michael’s Keenan Research Centre for Biomedical Science. Drs. Andras Kapus and Katalin Szaszi will also make use of the microscope to study cells that line other organs, such as epithelial cells in the kidney.

With TIRF, Dr. Lee’s lab is able to track several molecules, including insulin, albumin — a protein responsible for swelling during inflammation — and different types of cholesterols, as they’re shuttled through the cell.

The TIRF microscope will also allow Dr. Lee’s lab to test ways of preventing transcytosis.

“Our next focus is trying to find ways to stop molecules in the blood stream from hailing the cab,” said Dr. Lee. “For instance, if we can keep cholesterol from getting under the endothelium, we can stop it from building up in the wall of the blood vessel. This could stop the narrowing of arteries that leads to heart disease and stroke.”

About St. Michael's Hospital

St. Michael’s Hospital provides compassionate care to all who enter its doors. The hospital also provides outstanding medical education to future health care professionals in 27 academic disciplines. Critical care and trauma, heart disease, neurosurgery, diabetes, cancer care, care of the homeless and global health are among the hospital’s recognized areas of expertise. Through the Keenan Research Centre and the Li Ka Shing International Healthcare Education Centre, which make up the Li Ka Shing Knowledge Institute, research and education at St. Michael's Hospital are recognized and make an impact around the world. Founded in 1892, the hospital is fully affiliated with the University of Toronto.